378 FOSSIL TURTLES OF NORTH AMERICA. 



to have sloped steeply. The carapace is broadly archt along the median line and more sharply 

 archt from side to side. 



The nuchal bone occupied 100 mm. of" the free border; its maximum width is 120 mm.; 

 and its length is 1 10 mm. The neurals agree very closely with those of Leidy's plate xxx, fig. I, 

 of his Contributions. Not one is octagonal. The first is clavate; the second is hexagonal, and 

 comes into contact with both the second and the third pairs of costal plates; the third is quad- 

 rilateral and in contact with the third pair of costals only. The succeeding neurals are all hex- 

 agonal, and each is in contact with the corresponding pair of costals and with the pair 

 immediately in front. The anterior four neurals are longer than broad; the posterior four are 

 broader than long. 



Behind the neurals is a series of 3 suprapygals (fig. 474). The first, or most anterior, is 

 42 mm. long and 34 mm. wide. It is in contact with the eighth pair of costals. The second 

 suprapygal is bifurcate, as in Testudo, and the forks rest on the eleventh peripherals. The 

 third suprapygal is triangular, with a straight and broad base, and lies between the forks of 

 the second suprapygal. It is evident that there were three suprapygals in the specimen repre- 

 sented by Leidy, plate xxx, fig. I, of his Contributions, etc. 



The costals display only the earliest stages of the differentiation seen in the genus Testudo. 

 Only those of the third pair articulate with 3 neurals. The table herewith presents the widths 



of the upper and lower ends. Most of the costals are crost by 

 width wid h ' ow llc ^S es > which mark the stages of growth of the dermal scutes. 

 Costal. uppcrclu | lower end. The peripherals are relatively low, as compared with those 



of most species of the genus Testudo. Those of the bridge have 

 67 78 a height of about 80 mm., as do also those of the axillary and 



i 



inguinal regions. 



7 8 56 



74 67 



63 51 



44 5 



27 56 



4 7* 



The vertebral scutes are of moderate width and have 

 straight sides. The first, second, and fourth are each 106 mm. 

 wide; the third, ill mm.; the fifth, 179 mm. at its hinder 

 end. The first vertebral is 80 mm. wide at the anterior end. 

 The nuchal scute is 40 mm. long and about 17 mm. wide. The 

 sulcus between the marginal scutes and the costals follows closely 

 the suture between the underlying bones, except that it crosses the first peripheral some dis- 

 tance below its upper border. 



The plastron (plate 61; text-fig. 475) has an extreme length of 550 mm. The anterior end 

 projects about 35 mm. in front of the carapace. The central parts of the plastron are somewhat 

 concave. The anterior lobe is 175 mm. long and 246 mm. wide at the base. The free borders 

 are acute. The anterior lip projects slightly beyond the general contour of the lobe, and 35 mm. 

 beyond the line joining the points where gulo-humeral sulci cross the free border. Between 

 these points the lip is 1 18 mm. wide. On its superior surface the lip extends backward 75 mm. 

 The upper surface is slightly convex from side to side; the lower surface is nearly flat. The 

 anterior outline is rounded. 



The entoplastron is narrow in front and broad behind. The length in the median line is 

 1 15 mm.; the greatest breadth, 134 mm. 



The length of the posterior lobe is 157 mm.; the width at the base, 240 mm. The width 

 of the posterior notch is about 80 mm.; the depth, 30 mm. The fore-and-aft extent of the 

 bridge is 215 mm. The free edges of this lobe are acute. At the inguinal notch the border of 

 the hypoplastron is 36 mm. thick. From the summit of the wall thus formed the bone slopes 

 to the free edge at an angle of about 45. 



The gular scutes encroach somewhat on the entoplastron. The humero-pectoral sulcus is 

 tangent to the entoplastron behind. The pectoral scutes meet along the midline about 62 mm.; 

 the abdominals, 163 mm.; the femorals, 73 mm.; the anals, 43 mm. 



A specimen in the American Museum of Natural History, No. 1068, belonging to the Cope 

 collection, having a plastron 410 mm. long, agrees well with the preceding description. How- 

 ever, the anterior vertebral scute is urn-shaped, with an anterior width of 44 mm. and a pos- 

 terior width of 85 mm. 



Another shell obtained by the American Museum expedition of 1903, No. 6026, has a 

 length of 700 mm. The carapace is badly fractured and some portions of it are missing. The 



